/// <summary>
/// Repositions the mask in the DOM for nested modality cases.
/// </summary>
public void _repositionMask(Widget nextElem){}
/// <summary>
/// Updates the UI in response to a child being removed.
/// </summary>
protected void _uiRemoveChild(Widget child){}
/// <summary>
/// Default removeChild handler
/// </summary>
protected void _defRemoveChildFn(EventFacade @event, Widget child, Y_.DataType_.Number index){}
/// <summary>
/// Updates the UI in response to a child being added.
/// </summary>
protected void _uiAddChild(Widget child, object parentNode){}